The nature of mobile telecommunications systems is changing under the ever present influences of competition and improving technology. New digital services drive customer demand and mobile service providers are transitioning to faster digital networks to increase their bandwidth capacity while reducing bandwidth costs. Of course, these transitions have the added burden of maintaining or even improving current service levels during the transitional steps.
The original digital mobile networks focused on voice transmissions. Then, low bandwidth digital services such as text messages and e-mail were added. Currently, systems are being upgraded for high bandwidth multimedia applications. Throughout this transition, service providers need to maintain the same service availability and service quality that their customers have come to expect, or risk losing market share.
FIGS. 1 and 2 are an example of the evolution of one such GSM mobile network from a circuit switched voice system to a packet switched multimedia network. FIG. 1 shows a network 10, which has been upgraded from a circuit switched voice network with the addition of packet data transmission capability. The original network connected to a Public Switched Telephone Network (PSTN) 12, and included a plurality of Mobile Switching Centers (MSC) 14 which routed calls throughout a Base Station Controller (BSC) 16 and a Base Transmission Station (BTS) 18 to wireless mobile devices 20. Roaming users are accommodated by recording their presence in an (HLR) 22.
General Packet Radio Service (GPRS) was added to the original network by means of a (GGSM) 24 which made direct connection to a packet data network (PDW) 25. Packet data is coupled to BSC 16 through a Serving GPRS Support Node (SGSN) 26. This overlay data network effectively increased the bandwidth of the core network to allow high speed data transfer with an ‘always on’ connection. The restricting factor for end-to-end speech data transfers became the radio access network.
FIG. 2 shows the next step of transition with the addition of a high speed wireless interface in the form of wide band code division multiple access (WCDMA). This new interface includes a multiplicity of secondary transmission nodes 30 (known as Node B), which are typically co-located on existing BTS 18 towers. Signals are coupled to secondary nodes 30 through Radio Network Controllers (RNC) 32 which can handle more than one secondary node 30. Co-location of secondary nodes 30 on BTS 18 is possible because secondary nodes 30 work in a higher frequency band. Unfortunately secondary nodes 30 have a shorter signal range and typically enjoy less than optimal positioning on BTSs 18, which increases geographic coverage issues for service providers.
It should be noted that each of the different inter nodal links used in the described networks has a different functionality and uses a different signaling protocol that is handled by each intervening node. These different protocols add complexity to the networks, which makes fault analysis very difficult. For this reason, signaling analyzers have been developed to record the various signaling information in a database to thereby allow careful analysis of the cause of communications problems.
The new high speed wireless interface and the described co-location and coverage issues will require exceptional troubleshooting capability for the new wireless interface links. This capability will require extensive visibility of the signaling for those links and will also require network wide access to confirm the root cause of communications failures.